OFC 2021 Rump Session, Wednesday, 09 June 06:00 – 08:00 am PDT
Did the Optics Industry Blunder by Switching Intra-Datacenter Links from NRZ to PAM4?
Will More DSP like PAM6 and Coherent Follow, or Will WDM and Parallel Save the Day?
Session Organizer and WDM Team Captain: Chris Cole, II-VI Incorporated, USA
WDM Team Provocateurs: Shigeru Kanazawa, NTT, Japan; Boris Murmann, Stanford University, USA: Chris Pfistner, Avicena Tech, USA; Peter Winzer, Nubis Communications, USA
Session Organizer and DSP Team Captain: Ilya Lyubomirsky, Marvell, USA
DSP Team Provocateurs: Yi Cai, ZTE, USA; Dan Sadot, Ben Gurion University, Israel; Henry Sun, Infinera, Canada; Xiang Zhou,Google, USA
Description from WDM Team:
PAM4 was chosen for bandwidth limited electrical channels by the IEEE Ethernet Group in 2012. Modulation format for 50G λs was debated by the IEEE in 2015. Shannon provided clear guidance to stick with NRZ because the optical channel is limited by SNR and not bandwidth. Unfortunately, because the optics industry is the tail on the IC industry dog, PAM4 was chosen to reuse ASIC SerDes technology already in development. This unnecessarily and permanently locked in lower SNR and higher power for optical links. PAM4 50G λs will ship in the millions despite availability of mature 50GBaud technology which enables 50G NRZ λs. Shannon was again ignored by the IEEE for 100G λs and appears likely to be ignored for 200G λs. However, emerging applications not tied to Ethernet are returning to communication theory fundamentals and defining higher channel count lower-order modulation WDM and Parallel links.
Easing the chip-to-chip communication bottleneck by leveraging microLED display technology
High-speed optical emitters derived from GaN-based microLED displays can move data at much higher density and lower power than copper, bringing optical connections to the centimetre scale
BY BARDIA PEZESHKI, ROB KALMAN, ALEX TSELIKOV AND CAMERON DANESH FROM AVICENA
MOST OF THE ENERGY consumed in computing systems is not in the computation, but in moving data, and the longer the distance, the greater the challenge in terms of energy and density. At longer length scales, fibre optic links have replaced copper, but at short distances the significant amount of energy required to convert data back and forth between photons and electrons makes optical interfaces prohibitive.
Although it may raise a few eyebrows, at these shorter length scales, optimized optical emitters derived from GaN microLEDs could be a promising candidate for optical communications by leveraging their success in the display industry. Such a move could transform the $400 billion computer hardware industry and enable entirely new architectures for parallel computing, machine learning, and processors.